Wednesday, October 31, 2018

#167 - Monday, October 29, 2018 - Little Green Planets

On Monday night, my astronomy club held a late-season stargaze at a local school out in the back parking lot.  Despite relatively chilly temperatures in the upper 40s, there was an excellent turnout of about 100 people!  Mostly families with a wide variety of ages of kids.

I brought my usual outreach rig - my Celestron 8-inch Schmidt-Cassegrain on its Celestron NexStar SE mount, as well as my Celestron eyepiece kit.  I also brought my Oberwerk binoculars, but ended up not having time to set them up!  I forgot my stepstool, but I can reach the height of most kids simply by rotating the mirror diagonal down toward the ground and having them come around the side.  Then I can rotate it back up for the parents.

Since most of the shorter focal length scopes belonging to my compatriots were focused on Saturn (Dobsonians and refractors), I slewed my scope to Mars (the automated robotic slewing always has the kids delighted at how cool that is) since the 2,032 mm of focal length of that little orange tube can make Mars an appreciable diameter at the eyepiece.  Coupled with a 13mm eyepiece, you could see it as a nice, bright, reddish-orange disk.  When the seeing was good, you could just make out the southern polar ice cap.  This eyepiece also has some chromatic aberration, so the right edge looked bluish as well.  For the many folks whose first time it was seeing another planet through a telescope, though, that hardly matters.  Especially not to the young girl who excitedly declared after coming back for seconds, "I want to be just like you!" 💕

Since transparency was excellent and seeing was decent, I decided to try out my newest camera, an itty bitty Celestron NexImage 5MP color planetary imager I won at the Hidden Hollow Star Party.  I'd installed the software and tested it (just by shining light on it) in SharpCap last week, so it was ready to rock and roll.  When I cropped the image size to 1024x768, it was pretty speedy for USB 2.0 - a cool 27 fps average.  Not the blazing speeds of my ZWO ASI1600MM Pro with its USB 3.0 running at an 800x600 crop clocking in at 100+, but fast enough to be legal on most side streets.  I took one video on Saturn of 2,000 frames, and one on Mars.

As fast as the image collection was, however, RegiStax had a bear of a time dealing with that data.  I recorded in my usual SER format, which RegiStax has seemed to favor, but its debayering method for handling one-shot color data is apparently very slow.  Every time I scrolled a frame, I saw the sparser monochrome images first before they resolved into the color frame as the debayering was accomplished.  With my monochrome images, aligning and stacking takes a total of about 3 minutes top to bottom for each color channel.  These videos took over a half hour each to align and stack.

And then, it came out green!  Not only that, but you can see the pixel pattern - basically it looks like all of the red and blue pixels were just eliminated, leaving the green pixel array and a bunch of empty spaces.

I opened up the TIFF in Photoshop, and sure enough, there is zero data in the red and blue channels.  Looking at the histogram in RegiStax before saving shows the exact same thing.  Where'd my data go??

Mars was the same, although I didn't even bother with the wavelet deconvolution (sharpening):

Again, no red and blue.  For the record, the videos look fine when I watch them in the SER viewer app I have, and they also look fine during alignment & stacking in RegiStax.  It's not till after that the blue and red channels are cut!

I'll try again with these and mess with some settings, and update later if I'm successful. 

Saturday, October 20, 2018

#166 - Thursday, October 18, 2018 - Winter is Coming

We sort of skipped fall and started our nose-dive straight towards winter already - my windshield has frosted three times this week!!  And I have a strong dislike for cold weather (despite growing up in eastern Washington state).  The only redeeming qualities of winter are Christmas, cuddling with my cats under a snuggie with a cup of hot Earl Grey, and the Orion Nebula!  (Longer nights help too!)

We had a couple clear nights in the last week, but I just couldn't bring myself to go outside when it was near freezing, I'm just not ready yet!!  But the transparency was excellent on Thursday night (although the seeing was sketchy), so I decided to set up my 8-inch Schmidt-Cassegrain in the front yard to grab the nice waxing gibbous moon and rapidly-receding Mars before it gets too far west.

Me with my C8, and the Moon and Mars above

I started with Mars so that I wouldn't lose it behind the rooftop.  I looked at it with an eyepiece first, and while I was able to resolve it with my 6mm eyepiece, it was fairly grainy and I couldn't see much detail.  But sometimes the camera can do better, since you can average out and sharpen away atmospheric effects to some extent, so I hooked up my ZWO ASI1600MM Pro with my Astronomik LRGB filters and started recording.  It's pretty small in my camera's FOV, so I cropped the frame to 800x600, which allows the camera to push frames faster down the USB 3.0 connection.  Faster frame rates are great because you can get more frames in the moments of clarity.  

A combination of poor-ish seeing and the bad-ish tracking of my NexStar mount led to some ghosting in the final image, but it really isn't too bad!  You've got surface color variation and the southern polar ice cap.  Woot!

Date: 19 October 2018 01:05 UTC
Object: Mars
Attempt: 16
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron NexStar SE
Frames: R: 879/2015
G: 836/2035
B: 813/2025
FPS: 122
Exposure: R: 2 ms
  G: 2 ms
  B: 5 ms
ISO/Gain: 139
Stacking program: RegiStax 6

I recorded luminance frames too, but it turned out a little oversaturated, and the final image looked better without the luminance channel.  (More on how to take & process planetary images here).  

Then I turned my attention to the moon, and I first recorded a full-frame video (the moon doesn't quite fit in the FOV of my camera without a focal reducer on my C8, but I can get most of it).  I got into conversation with a passerby, and the video was taking a long time to record since full-frame means slower frame rate, and then my tablet died.  My ZWO draws so much power that the tablet will die if it gets below about 50% battery life, unfortunately.  So I plugged it in and started again, but it was recording suuuuper slowly because my hard drive was almost full (my Surface 3 only has 128 GB, and the Mars data took up a few gigs, and there were several gigs of Windows updates that needed to be cleared out), so I wound up not getting a complete video file.  

After I got everything re-started, I copied the Mars data to the SD card in my tablet and ran Windows' disk cleanup tool, and then captured some cropped lunar images at higher frame rates.  It was still slower than usual due to the low disk space.  With the atmosphere being swimmy, the images didn't come out great, but they came out all right.

Date: 19 October 2018 01:55 and 01:56 UTC
Object: Moon
Attempt: 25
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik L Type 2c 1.25" filter
Mount: Celestron NexStar SE
Frames: 1: 401/2009
2: 325/1561
FPS: 1: 63
 2: 23
Exposure: 5 ms
ISO/Gain: 0
Stacking program: RegiStax 6

I took one last data set as well on Mare Tranquillitatis, or the Sea of Tranquility.  You can't see the lunar lander of course (it's very hard for even moon-orbiting satellites to see), but X marks the spot!
Date: 19 October 2018 02:02 UTC
Object: Moon
Attempt: 25
Camera: ZWO ASI1600MM Pro
Telescope: Celestron C8
Accessories: Astronomik L Type 2c 1.25" filter
Mount: Celestron NexStar SE
Frames: 1393/2000
FPS: 35
Exposure: 5 ms
ISO/Gain: 0
Stacking program: RegiStax 6

I finally packed up and went back inside when my feet were starting to go numb inside of my wool socks and fur-lined slippers!  The only reason I was out there that long in the first place was because it wasn't windy.

Sunday, October 14, 2018

#165 - Sunday, October 7, 2018 - Chasing Clear Skies

All weekend at the Hidden Hollow Star Party, Sunday night was looking to be the most promising night, and some of the local astronomy club members were talking about staying another night.  I was planning on it, and I had extra food and clothes to do so.  But then I checked the forecasts for both there and home, and home actually looked more promising!  So I packed up Sunday morning and drove back, dropped off my personal gear, picked up my C8, and turned right around and went to the observatory!

The forecast wasn't perfect, but I was highly motivated to try after an energizing weekend talking about astrophotography and sharing that skill with others at the star party.  It turned out better than forecast - there were no real clouds around, although there was still a thin high haze.

Since I had fixed the declination axis backlash, I decided to try again with my Celestron 8-inch Schmidt-Cassegrain on my Celestron Advanced VX mount after some recent difficulties (here too) (and here), using the Lumicon off-axis guider I'm still borrowing.  However, my dec axis wound up a little tight after all the messing with it I did, so it was even harder to balance than normal.

Once I got everything up and running, I decided to image the Dumbbell Nebula, since it would be bright enough to push through the haze.  Pretty quickly upon starting up PHD, I saw some problems though - now the right ascension axis was showing some crazy backlash too, requiring a lot of steps to clear during calibration.  The two axes came out highly non-orthogonal, and they seemed to be error-ing in the same direction.  It was super weird.

I decided to try taking some subframes anyway, and unbelievably, they looked fairly decent...
1-minute subframe

5-minute subframe

Don't mind the little difference in target brightness between the two of them; the raw file viewer I use, AvisFV, auto-levels them for viewing purposes.

Zoomed out, they look all right, but if you zoom in, the stars are kind of icky.
Same 5-minute frame, zoomed in

So I went ahead and re-calibrated PHD, but it didn't make it through calibration - it got to like step 60 during the declination portion and had still only moved the target star only 18 pixels (it needs to move it 25), and it was like getting stuck there or something.  So I decided to turn off guiding in declination just to see what would happen, especially since my polar alignment went well.

My polar alignment must have indeed been good, since dec only drifted a little bit (the red line).  The frame came out looking about the same as the others I took, at 2 minutes.

I also tried just not guiding, but that one looked a little worse on a 2-minute frame.  I tried re-calibrating, but there was still some serious backlash in RA when it switched from moving the star east to moving it west.  So I'll need to open up the RA axis here soon and apply the same fix as I did for dec this weekend.

Since that wasn't working, at around 10 PM, I pulled off the C8 and put the Borg on instead.  That took about 35 minutes to do, including re-balancing and re-aligning.  But it was worth it because the calibration looked mountains better.

I met someone at Hidden Hollow who got their 9.25-inch Schmidt-Cassegrain to take multiple-minute unguided exposures on his AVX, so either I'm unlucky and got a crappy one, or he was very lucky and got an unusually well-machined one!  Very frustrating for me!

In any case, I decided to image the Dumbbell on the Borg anyway, even though it's a much smaller target for that configuration, since it was up high in the Milky Way and the sky was kind of hazy still.

Finally, at 11 PM, everything was up and running and ready to go, and I was acquiring my red data.  Guiding was a little messy due to the atmospheric conditions, but with the generous 2x1.5-degree field of view that my ZWO ASI1600MM Pro + Borg 76mm apochromatic f/6.6 refractor provides, those errors didn't show up, and I got nice round stars and nice detail inside the nebula.

Zoomed view of the Dumbbell Nebula, red channel.

The rest of the night went swimmingly, although the swimmingly icky atmosphere just got worse and worse as the Dumbbell sank closer to the western horizon.  I completed getting 15x3-minute frames per color channel by 1:20 AM, and I packed up and headed home.  

While I was processing my Hidden Hollow data on Monday, I also processed this dataset, and it came out pretty decently!  I didn't take luminance, so I created a synthetic luminance frame the same way I did here for the Eastern Veil Nebula.

Date: 7 October 2018
Object: M27 Dumbbell Nebula
Attempt: 11
Camera: ZWO ASI1600MM Pro
Telescope: Borg 76ED
Accessories: Hotech SCA field flattener, Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron AVX
Guide scope: Orion 50mm mini-guider
Guide camera: QHY5L-II
Subframes: R: 7x180s (21m)
   G: 11x180s (33m)
   B: 13x180s (39m)
   Total: 31x180s (1h33m)
Gain/ISO: 139 (unity)
Stacking program: DeepSkyStacker 3.3.2
Stacking method (lights): Median kappa-sigma clipping
Darks: 20
Biases: 20
Flats: 0
Temperature: -20C

Not mind-blowingly awesome, but really good considering the atmospheric conditions!  Now I just need to get everything optimized for trying again with the 8-inch.  I am bound and determined to have a lightweight, small-FOV imaging rig!  I know it can be done!!

#164 - Saturday, October 6, 2018 - Imaging Through Fog & Sog at Hidden Hollow (Night 3)

I slept in from Friday night's adventures at the Hidden Hollow Star Party, but not too long - only about 8:30 AM - because I needed to shower, eat breakfast, and attend the talk before my talk, which was scheduled for 10:45 AM.  The talk before mine, starting at 9:30, was about the International Dark-Sky Association.

As I was getting set up after that talk, suddenly the projector died.  We worked on figuring out what was wrong with it when we realized that the lights had also gone out and my laptop wasn't charging - the whole building lost power!  And we found out that actually the whole camp had lost power.  Crap!  Luckily, someone down the hill at the lodge had a generator, so we moved the whole operation down there.  It was loud in the lodge with other people eating lunch and talking, so I had to talk loud, which luckily I'm pretty good at.

My talk was on "Astrophotography Without a Telescope," which was great for this star party because it's mostly comprised of visual observers, many of whom have some interest in trying astrophotography but don't really know where to start.  I talked about things you can do with just a DSLR and a tripod first, like star trails, timelapse, and short-exposure (15s or less) ultra-widefield.  Then I talked about tracked exposures using something like the Vixen Polarie or the Skywatcher, as well as piggybacking onto a telescope on a tracking mount.  I need to update the timelapse post to include using the Windows app Timelapse Deflicker, which has been awesome, and I need to write one about tracked and piggybacked configurations.  The talk went well, and hopefully now more of the folks there will give it a try!

As night fell on the third night of the Hidden Hollow Star Party, it was miraculously kind of clear again, except some clouds skirting the horizon.  Off to the north, we saw nearly-continuous flashes of lightning, but it looked like it was mostly moving eastward, and we couldn't hear the thunder, so I went ahead and pulled the cover off my scope.  I had a few folks around my rig, and I showed them how I polar align, align, and set up guiding.  Polar alignment went well - I was able to get within just a couple arcseconds of the pole.  Woot!  (Also getting the paid version of SharpCap to get access to the polar alignment routine is 100% worth the $15/year fee).

The bright star near the top labeled "a UMi" is Polaris, the North Star.  As you can see, it's not quite at the North Celestial Pole, only close to it.

Shortly after I slewed to the Western Veil Nebula and calibrated PHD for autoguiding, however, the lightning started to get very close and we heard some thunder as the storm turned south.  I quickly homed the scope, covered it, threw my tablet into my accessory bin, latched everything up, and ran inside the nearby education building just as it started to rain.  Darn!

Inside, someone had started up The Martian on the projector screen, so I watched the second half of that, and then poked my head back outside to see how the weather was.  It had cleared up again, I was back in business!  It took only 5 minutes for me to uncover the scope, re-connect my tablet, slew to the Western Veil Nebula, and start acquiring images.  Since I had only one night left, and the sky conditions weren't great, I decided just to take red, green, and blue data, and no luminance.  There was also a ground-level fog that I was looking through.  But I wanted to see what I could get anyway.

I went and sat inside because it was so wet outside, both from the rain and the very high humidity.  When I came back to check later, I discovered I'd lost about 15 minutes worth of frames when my mount randomly stopped tracking.  Either that, or PHD got crazy and guided away, or something like that.

Luckily, I just did a Precise Goto and got the target back in the center of the frame, and everything was fine after that.  Weird.

Around 1:30 AM, it actually cleared out pretty well, and the sky looked great.  But that was short-lived; at 2 AM, the fog came in thick, and I had to throw in the towel.  But I had captured 15x180s frames on each RGB channel, so I could probably get something out of it.

After I got back from Hidden Hollow, Monday was a holiday, so I spent the day processing data.  This dataset proved a little difficult, as I imagined.  I had to ditch some frames for poor tracking when the guide star was lost due to bad atmosphere.  They were also fairly noisy because I accidentally left the gain at 300 from when I was doing polar alignment and wanted short exposures to make it go quicker.  

First, I had stacked the frames in DeepSkyStacker using the "median kappa sigma clipping" algorithm and a 5% star detection threshold, but the final image came out prettttty noisy, and it also had a high background from the fog.  So I stacked the RGB images each again with my other favorite algorithm, "auto-adaptive weighted average," and a higher star detection threshold of 10% (the 5% was giving me like 10,000+ stars, which I didn't really believe).  These were less noisy, although of course the background was still high.  The target is just a little too big for synthetic flats to work well, so there's some glow toward the center, but really this came out rather well for the atmospheric conditions!  If I really stretch the image, you can see some of the Pickering region below the main part of the Western Veil.
Date: 6 October 2018
Object: NGC 6960 Western Veil Nebula
Attempt: 5
Camera: ZWO ASI1600MM Pro
Telescope: Borg 76ED
Accessories: Hotech SCA field flattener, Astronomik LRGB Type 2c 1.25" filters
Mount: Celestron AVX
Guide scope: Orion 50mm mini-guider
Guide camera: QHY5L-II
Subframes: R: 13x180s (39m)
   G: 9x180s (27m)
   B: 14x180s (42m)
Gain/ISO: 300
Stacking program: DeepSkyStacker 3.3.2
Stacking method (lights): Auto-adaptive weighted average
Darks: 20
Biases: 20
Flats: 0
Temperature: -20C

So yay, I got something out of that soggy weekend!  I've also got a bunch of frames from my DSLR attached to my Vixen Polarie of the Cygnus region, but I didn't happen to have dark frames with the same exposure time, and the nighttime temperature went from the 60s straight down to the upper 30s, totally skipping the low 50s it was when I originally acquired that data on Thursday night, so I'm going to have to wait for it to warm back up a bit.

And finally, I got some timelapse images as I always do, so here's the video!

There's a sequence in there where it started to rain like crazy.  It had looked like it was going to rain earlier, but I still wanted to image it, so I ran back up the hill and grabbed the water-resistant cover that came with my camera bag.  I secured it to my DSLR with rubber bands and gaffer's tape.  It worked great!

I had to jury-rig the lens hood to that lens though - the lens hood belongs to my 55-200mm lens, and the 18-55mm stock lens doesn't have a connection for a lens hood.  Again, gaffer's tape to the rescue!  It kept most of the rain off the lens, although I had to wipe off a few drops after the rainstorm (as you can see in the video).  Now I have a way to image during possible rain and not have to worry about the camera, woot!

Saturday, October 6, 2018

#163 - Friday, October 5, 2018 - A Foggy Night at Hidden Hollow (and I fixed my mount!!)

It was a chilly, rainy day at Hidden Hollow Star Party!  But it didn't rain all day, so between rain showers, I decided to try out the backlash fix for my Celestron AVX mount that I found in this YouTube video.

First, I needed to remove the casing around the declination axis, which was held on with Phillips screws.  Unfortunately, one of them is placed such that I couldn't get a screwdriver in straight because the mount head was in the way, so I had to remove the mount head.  I was working quickly because of the threat of rain, otherwise I would have taken more pictures and video - sorry!

Once that was removed, I powered on the mount and slewed in dec at slow speed so I could see how things were looking.  Sure enough, the backlash was very obvious - the motor drive gear had to turn a fair distance before engaging the worm wheel gear.

I removed the motor drive gear as shown in the YouTube video with a small hex wrench, and then I loosened the three hex bolts (just loosened a bit, not much) that hold the motor in place.  Then I put the motor drive gear back on, and pushed the motor closer to the worm wheel gear.  I tightened up the motor drive gear onto the shaft, and checked how it meshed with the worm wheel gear - there was still some gap, so I pushed it in a bit further.  I checked whether there was still backlash by slewing at slow speed (speed 3), and sure enough, the motor drive gear engaged the worm wheel gear right away!  I took off the gear, tightened the motor bolts back up, and then put the gear back on.  Then I slewed around at high speed to make sure it wasn't binding anywhere.  Then I put the case back on so I could put the mount head back on and see that slew around.  Everything was looking good until it started whining loud - the dec clutch hit the casing!  For some reason, I had to turn it down more than usual to tighten it.

Video showing the backlash before and after my fix.

I was about to start figuring out that problem when it started to rain hard, all of a sudden!  I quickly threw the cover over the mount, but the telescope with cameras attached was still sitting on the table.  I quickly grabbed it, threw my computer's dew towel over it, and dashed down the hill to my car, since it was too long to fit into my accessory bin.  Then I sprinted back up the hill to grab my DSLR and Vixen Polarie, which were still out from doing a timelapse run earlier.  They plus my intervolemter were pretty soaked, so I laid them out to dry in my car and ran back up the hill one more time to the education building.  I was thoroughly soaked!

The rain only lasted about 20 minutes or so.  After it ended, I put the mount back together with the scope, but since it was still threatening to rain some more, I decided to postpone working on the dec clutch problem until later that night.  

When I returned to the observing hill that evening, the sky looked fairly clear, which was surprising, but a fog had formed from the ground up to about 20 feet or so.  Unfortunately, the temperature was actually increasing slowly all night, so it stayed at 100% humidity all evening, and that fog never lifted.

However, since the sky was clear, I was able to test out whether my backlash fix worked.  But first, I needed to fix my dec clutch.  I removed the mount head from the mount again so I could see why I was having to tighten the clutch more than usual.  I thought at first that maybe the cylinder that the mount head attaches to was not quite circular, so I rotated the mount head with respect to the cylinder (the four bolt holes used to attach it are square, so you can rotate it 90 degrees at a time).  No luck though - I still had to turn the dec clutch far enough that it would hit the casing.

I got someone else to come over and look at it, and he suggested I remove the whole knob (it has a Phillips head screw holding it on).  Once I removed it, I could see that it had little notches in it that would allow you to orient it any number of ways with respect to the clutch bolt, so I just put it on rotated higher up and put the Phillips screw back in.  Now I could tighten it, and it wouldn't turn so far down as to hit the casing.  Fixed!

I re-polar aligned and re-aligned, re-focused, and slewed again to the Western Veil Nebula.  I calibrated PHD, which still showed a lot of backlash in dec during calibration, but then the guiding graph looked pretty flat and not crazy like before.  I got sidetracked in conversation, but then I checked on the incoming 3-minute luminance frames, and the stars looked round!  And the guide graph looked pretty good!

Weird-shaped stars because of bad guiding because of bad backlash in declination

Basically what stars should look like (ignore the noise, it's a raw frame)

Frame after frame looked this good.  It was hard to see the Western Veil Nebula itself due to the fog, but I had accomplished my goal for the evening, which was to see if my backlash was fixed!  Success!  I might have shed a tear or was beautiful...

After sitting inside and chatting for a while, I poked my head back out later, but the fog was still just sitting there.  I also tried to image the Andromeda Galaxy area with my Nikon D5300 on my Vixen Polarie, but I was having a hard time focusing - my 55-200mm lens is very touchy on focus.  I finally gave up and got into bed by about 1:30 AM.  I needed to be up around 8:30 the next morning to give my talk - "Astrophotography Without a Telescope."  

So I won't have an image, but at least I fixed my mount! :D  Now I need to figure out how long I can guide for.  Hopefully I can get a couple stars tonight to test that on.  Forecast is looking dicey.  On top of that, the scissor lift to look through Hidden Hollow's 36-inch reflector "Big Blue" is broken! :(

#162 - Thursday, October 4, 2018 - First Soggy Night of Hidden Hollow

It's that time of year again - the Hidden Hollow Star Party!  This small star party in northern Ohio is always a fun time, and bonus, they have an enormous 36-inch reflector called "Big Blue."  However, the weather is always dicey and unpredictable!

The Clear Sky forecast showed it clearing up around 2 PM, but it was full-on clouds all afternoon and into the evening.  After arriving around 5 PM and chucking my stuff into one of the cabins (it's hosted at a summer camp), I got my gear set up in the shadow of the Big Blue observatory dome.  After heating up some leftovers for dinner (there's a food truck, but they weren't open yet), I hung out in the education building to watch Avatar on the projector screen.

A little after 8 PM, I poked my head outside and saw Mars!  I looked around, and a good portion of the sky had cleared up!  So I ran back inside to alert the small contingent who were also there a night early, and I yanked the cover off my scope and started getting focused and polar aligned.  During focusing though, I quickly ran into a problem.  I was trying a different configuration of my imaging train so that I could avoid the problem of having to attach my Hotech self-centering field flattener to the telescope's 2-inch eyepiece adapter, since the self-centering thing doesn't quite work right and is just a little bit too large to fit properly into the eyepiece adapter. I really have to jam it in there, which means I have to screw on my entire imaging chain, which is difficult to do.  So I re-arranged it with a few new components I bought: camera-field flattener-filter wheel-2 inch eyepiece connector.  However, due to the length of the field flattener's tube versus the length of the M48-to-2 inch eyepiece adapter I used to attach it to the filter wheel, it put the camera too far back from the scope to focus.  So I had to put it back to the way I had it previously: camera-filter wheel-field flattener.  Since my dovetail bar extends longer than the telescope on the back end (due to placement of the holes on the dovetail bar), I have to take the telescope out of its clamps in order to screw the whole thing onto the telescope, since otherwise the filter wheel hits the dovetail as I rotate it around.  Basically, it's a hue massive pain.  But I need the field flattener, otherwise like half of the image is warped (like this example from the 2017 Texas Star Party - scroll down to the image of the Trifid and Lagoon Nebulae).

Anyway, I got that re-done, polar aligned and aligned without issue, and then started imaging the Western Veil Nebula, which was nice and high.  I took the first two frames, and guiding looked pretty all right.  It was time for a meridian flip already, so I did that, re-centered with Precise Goto, and pressed on with the luminance frames.  I went and chatted with several other attendees.

It was a chilly night!  Already 53 degrees by 9:30.

I came back later, and upon closer inspection, my stars looked kind of funny.

All of my frames were looking like this.  Usually when it's a tracking or guiding issue, the stars look weird differently in each frame as they streak one way and then another, but that wasn't the case here - they all looked like this.  So I thought that maybe my field flattener wasn't square with the camera and the telescope.  I tightened up a few connections, but my frames still looked bad.

Also, if I left the guiding alone and didn't baby-sit it by re-acquiring the guide star every once in a while, my guiding looked like this:

It's a continuation of the backlash problems I've been having with the declination axis of my Celestron AVX mount.  I could also tell because during calibration, after moving the scope north and then turning around and moving the star south back into the crosshairs, there was still a lot of space left where the mount had to catch up.  

After the issues I had last month, I did a little Googling to see what could be done about backlash, and I found a YouTube video that showed a simple fix of moving the motor drive gear in closer to the worm wheel so that the drive gear didn't have to rotate so far to engage the worm wheel.  It's by Broke Astronomer here.  It didn't require taking apart too much of the mount, and looked like a fix that had a low risk of breaking anything, so I decided I'd give it a try the next day.

In the meantime, I tried backlash compensation in PHD, but it wasn't much better.

While my stars were looking like crap on my AVX, I also set up my Vixen Polarie with my DSLR with my 55-200mm lens at 55mm to image the Cygnus region.

The Vixen Polarie is a simple star tracker that you point at the North Star, and then you can point your DSLR anywhere and it will track at sidereal speed, allowing you to take long exposures in a very portable setup.  The handwarmer rubber-banded to my lens helped keep the dew away.

I got quite a few clouds rolling through, but still managed to get about 60x2-minute frames that were mostly cloud-free.  I haven't stacked it yet because I forgot to collect darks, and it was 50 degrees F - too warm for a fridge, but too cold for a space in a house.  So I'll just have to wait until it's cool again at night to capture those dark frames.  But here's a single frame:

The brighter star in the middle is Deneb, and the dimmer one is Sadr.  It doesn't look like much now, but after I stack it, it'll be awesome!

[Update October 20, 2018]:

Here's the stacked image!
Date: 4 October 2018
Object: Cygnus widefield
Camera: Nikon D5300
Telescope: Nikon 55-200mm lens at 55mm, f/4
Accessories: N/A
Mount: Vixen Polarie
Guide scope: N/A
Guide camera: N/A
Subframes: 60x120s (2h)
Gain/ISO: ISO-1600
Stacking program: DeepSkyStacker 3.3.2
Stacking method (lights): Auto-adaptive weighted average
Darks: 30 (48F)
Biases: 20
Flats: 0
Temperature: 48-50F

I wasn't able to pull a ton of contrast from it in Photoshop, primarily because of the thin high clouds that were sweeping through (I had to delete a lot of frames before I got to the 60 that make this image), but the red H-II regions (hydrogen alpha) came through, which was exciting!  Those are head to get on an unmodified DSLR.  I'll try again sometime in PixInsight.  The color balance isn't quite where I'd like it either, but getting that right with a DSLR (which for me always come out green) is tough!

[End update.]

After 2:30 AM, I moved the DSLR over to see the Orion constellation, but by then there were a lot of clouds rolling through.  I finally went to bed around 3:30 AM, after packing up the DSLR and Polarie and putting a cover over my telescope.  Everything was pretty soaked with dew.

The night was much clearer than predicted, which was great!  Too bad my mount was still being ridiculous.  I'm getting pretty tired of constantly fighting my mounts!